Heat the oil in a large skillet, and use it to fry the onion and carrots for 5 minutes, then stir in the sausages and fry until they begin to brown (around 10 minutes).
Stir in 600 ml water and bring the mixture to a boil.
Reduce to a simmer and stir in the olives. Cook for 5 minutes or until heated through. Season with salt and black pepper.
Laddle into soup bowls (at this point with drain off the soup and stir fry it again to dry it a little, personal taste), garnish with the parsley.
Serve with the lemon slices.